Abstract
Panax ginseng C.A. Meyer is a traditional medicinal herb that produces bioactive compounds such as ginsenosides. Here, we investigated the diversity of ginsenosides and related genes among five genetically fixed inbred ginseng cultivars (Chunpoong [CP], Cheongsun [CS], Gopoong [GO], Sunhyang [SH], and Sunun [SU]). To focus on the genetic diversity related to ginsenoside biosynthesis, we utilized in vitro cultured adventitious roots from the five cultivars grown under controlled environmental conditions. PCA loading plots based on secondary metabolite composition classified the five cultivars into three groups. We selected three cultivars (CS, SH, and SU) to represent the three groups and conducted further transcriptome and gas chromatography-mass spectrometry analyses to identify genes and intermediates corresponding to the variation in ginsenosides among cultivars. We quantified ginsenoside contents from the three cultivars. SH had more than 12 times the total ginsenoside content of CS, with especially large differences in the levels of panaxadiol-type ginsenosides. The expression levels of genes encoding squalene epoxidase (SQE) and dammarenediol synthase (DDS) were also significantly lower in CS than SH and SU, which is consistent with the low levels of ginsenoside produced in this cultivar. Methyl jasmonate (MeJA) treatment increased the levels of panaxadiol-type ginsenosides up to 4-, 13-, and 31-fold in SH, SU, and CS, respectively. MeJA treatment also greatly increased the quantity of major intermediates and the expression of the underlying genes in the ginsenoside biosynthesis pathway; these intermediates included squalene, 2,3-oxidosqualene, and dammarenediol II, especially in CS, which had the lowest ginsenoside content under normal culture conditions. We conclude that SQE and DDS are the most important genetic factors for ginsenoside biosynthesis with diversity among ginseng cultivars.
Highlights
Panax ginseng is a medicinal plant that has long been used as a tonic agent throughout Asia, including Korea and China (Jia et al, 2009)
These results indicate that PPD/PPT ginsenosides are the main contributors to the metabolic differences in adventitious roots among these cultivars
We focused on the genetic component of ginsenoside accumulation by using five genetically fixed inbred cultivars, CP, CS, GO, SH, and SU (Kwon et al, 2001; Ahn et al, 2008; Lee et al, 2008) and isolating ginsenosides from in vitro cultured adventitious roots grown under a controlled environment
Summary
Panax ginseng is a medicinal plant that has long been used as a tonic agent throughout Asia, including Korea and China (Jia et al, 2009). Dozens of ginseng accessions have been bred through pure line selection from three local landrace populations (Jakyung, Chungkyung, and Hwangsook) and registered as cultivated varieties (cultivars) in Korea (Kim et al, 2012). These cultivars exhibit different morphological and physiological characters (Kim et al, 2012; Lee et al, 2015), as well as different metabolite accumulation patterns (Ahn et al, 2008; Kim et al, 2009; Lee et al, 2011; Cho et al, 2012). PPD and PPT are glycosylated to produce various types of ginsenosides (Kim et al, 2014)
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